This invention relates to a fastening means; more particularly the invention relates to a unitary, molded, self-locking plastic fastener.
Various fastening means are known for joining two workpieces together or for anchoring a screw or bolt to a workpiece. For example, U.S. Pat. Nos. 2,887,926; 3,143,916; 3,313,083; and 3,601,869 all describe collapsible plastic fasteners adapted to receive a self-threading screw and fold on to itself with the exterior perimeter expanding when the self-threading screw is advanced through the fastener. Other plastic fasteners are designed to axially collapse on to themselves. For example, U.S. Pat. No. 3,443,473 shows a hollow rivet fastener for use between opposing skins of a sandwich construction. The fastener of this patent axially collapses between the two layers of the sandwich to provide strengthened columnar support on the unsupported portions of the sandwich faces.
Other fasteners such as toggle bolts or anchors are known in which the advancement of a self-threading screw or an anchor bolt into the anchor expands the anchor and forces the anchor into the surrounding medium. For example, as shown in U.S. Pat. Nos. 3,472,111 and 3,735,665 expandable anchor bolts are shown in which the advancement of a bolt or screw into the anchor causes an expansion of the anchor into the surrounding medium and the resulting locking of the anchor into the medium.
Other fastening devices are shown in U.S. Pat. Nos. 3,270,793; 3,521,521; and 3,683,740.
Each of these various anchors and fasteners while useful for different functions operate by expanding a portion of the fastener to grip the substance in which the fastener is inserted or to expand behind the object to which the fastener is inserted and thereby lock the fastener in place. In the operation of the prior art fasteners, however, once the screw or bolt is backed out of the fastener the fastener may no longer hold. This occurs because the fasteners lack any internal self-locking means to retain the fastener in its expanded operable position. Thus, for example, in a unitary axially expanding fastener, shown in U.S. Pat. No. 3,313,083, once the self-tapping screw is backed out of the plastic fastener, there is no means within the fastener to lock it in its expanded position and to prevent it from assuming its former condition.
Accordingly it is an object of this invention to provide a unitary, deformable plastic fastener which once inserted into a body and expanded into its operative, fastening mode will retain its holding capacity after the screw or other threaded member is withdrawn from the fastener.
A still further object of the present invention is to form the fastener from deformable, unitary molded plastic or nylon material.
Another object of the present invention is to provide a plurality of fasteners which may be locked in place by a single screw, which is inserted into and then removed from each fastener after the fastener is locked in place.